Fluid-solid reaction systems, such as gas-solids reaction systems, often require the solids to be retained in early stages of the reaction system while the vapor product, essentially free of solids, is processed in downstream equipment. It is desirable in these systems that the solids be as completely removed as possible from the vapor before transferring the vapor to the downstream equipment. In reaction systems that use small particle catalysts, the loss of catalyst particles during operation means that additional catalyst has to be added during operation to make up for the catalyst loss. Particularly in cases where the cost of catalyst is high, even marginal improvements in solid particle retention can lead to substantial reductions in operating costs. The problem of solid particle loss can be compounded if the solid particles are susceptible to attrition, such as by shattering or otherwise breaking into smaller pieces. Smaller particles are typically more difficult to separate from a gas-solids flow, so the attrition of large particles into smaller particles compounds the problem of effectively separating solids from a gas flow. As a result, reactor designs and separation methods that tend to reduce particle attrition while improving separation efficiency are desirable.
U.S. Patent Application Publication 2004/0076554 describes a riser reactor system having multiple risers that feed into a separation vessel. The multiple risers are located outside of the separation vessel. The top of each riser is connected to the separation vessel using a single deflecting member in the form of a curved or angled connector.
U.S. Pat. No. 4,664,888 describes a riser reactor that feeds a gas-solids flow into a separation vessel through a plurality of rough cut separators. Each of the rough cut separators cause the output of the riser to undergo a tight, 180 degree downward turn after exiting the riser.
U.S. Pat. No. 4,313,910 describes a riser reactor that feeds into a separation vessel after being deflected by a semicircular cap. A substitute gas is introduced into the gas-solids flow in the semicircular cap to replace the gas from the riser reactor.
U.S. Pat. No. 5,190,650 describes a riser having a plurality of openings around the circumference of the riser at its discharge end. The openings in the riser are allow gas to escape tangentially from the riser. Gas discharged through an opening passes through a curvilinear tube and tangentially enters a cyclone separator.
What is needed is a system and method for reducing or minimizing the attrition and loss of solid particles during separation from a gas-solids flow. The system and method should be compatible with conventional riser designs as well as conventional separators, such as cyclone separators. The system and method should also allow a gas-solids flow from a riser to be closely coupled with multiple separation devices, such as cyclone separators.